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# 11
03-28-2012, 09:17 AM
A generation ship is far from the best option for interstellar travel, even taking into account our rather primative technologies. The best aproach would be to accelerate continously Reaching relativistic speeds within a few months, and providing the advantage of time dilation, making the trip duration far shorter for those making the journey than it would be to outside observers.
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# 12
03-28-2012, 09:18 AM
Of course sleeper ships are more fun. There's not much of a downside to going on a sleeper ship, and you get to enjoy the fuits of your investment. That's why asking about a generational ship is much more interesting.

Quote:
A generation ship is far from the best option for interstellar travel, even taking into account our rather primative technologies. The best aproach would be to accelerate continously Reaching relativistic speeds within a few months, and providing the advantage of time dilation, making the trip duration far shorter for those making the journey than it would be to outside observers.
The trip to Kepler 22b would still be 600 years at the speed of light.
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# 13
03-28-2012, 09:24 AM
Quote:
Originally Posted by Ertwin View Post
The trip to Kepler 22b would still be 600 years at the speed of light.
You're forgetting time dilation. For example, at .9c, the relativistic factor is roughly 2.29. It would take 667 years from an outside point of reference, but only 291 years from an internal point of reference. At .95 c the relativistic factor is 3.2. So while the travel time is 631.5 years, it would only be 197 to those on the ship.
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# 14
03-28-2012, 09:32 AM
Quote:
Originally Posted by Ertwin View Post
Of course sleeper ships are more fun. There's not much of a downside to going on a sleeper ship, and you get to enjoy the fuits of your investment. That's why asking about a generational ship is much more interesting.



The trip to Kepler 22b would still be 600 years at the speed of light.
Not for those on board the vessel due to time dialation that can be calculated by findiing the Lorentz Factor, which will make both the distance traveled and the time it took to travel the distance seem much smaller to the passengers of any such vessel.

Time Dilation
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# 15
03-28-2012, 09:35 AM
Quote:
Originally Posted by hevach View Post
You're forgetting time dilation. For example, at .9c, the relativistic factor is roughly 2.29. It would take 667 years from an outside point of reference, but only 291 years from an internal point of reference. At .95 c the relativistic factor is 3.2. So while the travel time is 631.5 years, it would only be 197 to those on the ship.
At .999 c it is the Lorentz factor is 22.3 and so to the passengers aparent travel time sould be just under 30 years. Getting even closer to the speed of light makes the Lorentz Factor much larger, making aparent travel time much shorter.
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# 16
03-28-2012, 09:43 AM
I think you missed a 9. At .99 it's only 7.08.
Handy toy for the discussion: http://www.1728.org/reltivty.htm (decimal portion of c int he top box, click the C=1 button, bottom number)

Though these are only partial calculations, assuming you instantly accelerate and then simply slam into the planet at full speed upon arrival. In reality you'd have to spend the first half of the trip building up to these speeds and the second half shedding it again so you're below escape velocity when you arrive, at which point you spend a pretty substantial portion at each en dof the trip with a Lorentz factor somewhere closer 0.
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# 17
03-28-2012, 09:48 AM
Quote:
Originally Posted by hevach View Post
I think you missed a 9. At .99 it's only 7.08.
Handy toy for the discussion: http://www.1728.org/reltivty.htm (decimal portion of c int he top box, click the C=1 button, bottom number)

Though these are only partial calculations, assuming you instantly accelerate and then simply slam into the planet at full speed upon arrival. In reality you'd have to spend the first half of the trip building up to these speeds and the second half shedding it again so you're below escape velocity when you arrive, at which point you spend a pretty substantial portion at each en dof the trip with a Lorentz factor somewhere closer 0.
You correct I left out a 9, I will correct.

And you are correct about the acceleration/deceleration, but if one were intelligent about it they would probably slingshot off of stars providing a much higher rate of acceleration, and probably calculate paths to provide gravitational braking as well.

With that distance and the use of the gravitational fileds of star systems they may get closer to c than .999.

There would be a lot involved in calculating the optimum trip. As you reduce the aparent travel time you reduce the amount of materials that you must carry, but you increase the amount of energy required to reach those velocities. However, the hassles of keeping equipment functioning over multiple generations makes multi-generational travel problematic.

I cannot imagine the trip lasting more than about 30 years from the passengers perspective. At 30 years you can have a small group of crew and educators, and children as the eventual colonists. It would be best to have more female children than mle children the exact ratio determined by travel time and number of colonists, Adult crew would probably be close to 50/50 or alll one gender or the other..
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# 18
03-28-2012, 09:49 AM
Quote:
Originally Posted by Ertwin View Post
No cryo systems. You live on the ship, and raise a family, then in a couple thousand years, your decendents colonise the planet.
What's the point of that??

Quote:
Originally Posted by hevach View Post
You're forgetting time dilation. For example, at .9c, the relativistic factor is roughly 2.29. It would take 667 years from an outside point of reference, but only 291 years from an internal point of reference. At .95 c the relativistic factor is 3.2. So while the travel time is 631.5 years, it would only be 197 to those on the ship.
I saw on a Stephen Hawking documentary that if the ship reached 99% of light speed, the time dilation would be so that the crew would only experience a day for every year of travel. So 600 years = 600 days for the crew.
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# 19
03-28-2012, 09:50 AM
Sorry had a brainfart about the relativity. However moving at relativistic speeds is still a bad idea. At those speeds, particles of dust would hit with the force of a warhead.
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# 20
03-28-2012, 09:54 AM
Quote:
Originally Posted by Ertwin View Post
Sorry had a brainfart about the relativity. However moving at relativistic speeds is still a bad idea. At those speeds, particles of dust would hit with the force of a warhead.
Not if we have inertial dampeners.
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